This invention relates to a photographic optical bench that is used for transferring an image from a transparent photographic medium such as a negative, or transparency to a secondary photographic medium to be exposed. The secondary photographic medium may be a photosensitive paper to produce a print of the negative or transparency, may be a photographic film to produce another transparency, an internegative, or a single colour separation from a multicolour negative or transparency. The image on the secondary photographic medium may be of the same size when, for example, duplicating the transparent photographic medium or it may be enlarged or reduced in size.
When a transparent photographic medium is illuminated by a condenser lens system any imperfections such as scratches on the film stock, dust, and even the grain structure of the photographic emulsion are brought into sharp focus on the secondary photographic medium. Thus, to avoid this degradation in the image quality on the second photographic medium a diffuse light source is normally used to illuminate the transparent photographic medium. This results in an overall loss of sharpness and definition in the image formed on the secondary photographic medium but this is usually considered preferable. Conventional photographic benches usually use a continuous source of illumination such as a tungsten halogen bulb located behind a diffusing screen to illuminate the transparent photographic medium with light scattered from the diffusing screen. Usually provision is made for introducing one or more differently coloured filters into the optical path to enable the secondary photographic medium to be exposed to the image carried by the transparent photographic medium with light of different colour.